Board Thread:General Discussion/@comment-26222858-20150917141812/@comment-6769189-20151009011835

An object is only a manifestation when it comes from someone/something.

Dante's default(Rebellion) DT has red and black designs. The only time these black markings change is when another DA's energy is flowing through them. Vergil shares this trait, this means Yamato gives Vergil access to his DT.

Vergil had Yamato since he was a young child, so his power and Yamato's power most likely have become closely related and using Yamato brings out his "Vergil DT". Another possibility is that Vergil and Yamato resonated when he was young/a baby, prompting Sparda to leave Yamato for him because Vergil and Yamato's energies already melding/working well with each other. We have to also take into account that we don't know if Yamato was once a demon. It may just be a weapon that is demonic in nature that doesn't cary any specific traits to pass on to the user. We just know that it holds the element of Darkness.

This would make Yamato essentially a battery for Vergil and Nero, bringing out their natural DT's with the added sheath.